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100 lines (92 loc) · 2.34 KB
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/* -*- Mode: js; js-indent-level: 2; -*- */
/*
* Copyright 2011 Mozilla Foundation and contributors
* Licensed under the New BSD license. See LICENSE or:
* http://opensource.org/licenses/BSD-3-Clause
*/
/**
* A data structure which is a combination of an array and a set. Adding a new
* member is O(1), testing for membership is O(1), and finding the index of an
* element is O(1). Removing elements from the set is not supported. Only
* strings are supported for membership.
*/
class ArraySet {
constructor() {
this._array = [];
this._set = new Map();
}
/**
* Static method for creating ArraySet instances from an existing array.
*/
static fromArray(aArray, aAllowDuplicates) {
const set = new ArraySet();
for (let i = 0, len = aArray.length; i < len; i++) {
set.add(aArray[i], aAllowDuplicates);
}
return set;
}
/**
* Return how many unique items are in this ArraySet. If duplicates have been
* added, than those do not count towards the size.
*
* @returns Number
*/
size() {
return this._set.size;
}
/**
* Add the given string to this set.
*
* @param String aStr
*/
add(aStr, aAllowDuplicates) {
const isDuplicate = this.has(aStr);
const idx = this._array.length;
if (!isDuplicate || aAllowDuplicates) {
this._array.push(aStr);
}
if (!isDuplicate) {
this._set.set(aStr, idx);
}
}
/**
* Is the given string a member of this set?
*
* @param String aStr
*/
has(aStr) {
return this._set.has(aStr);
}
/**
* What is the index of the given string in the array?
*
* @param String aStr
*/
indexOf(aStr) {
const idx = this._set.get(aStr);
if (idx >= 0) {
return idx;
}
throw new Error('"' + aStr + '" is not in the set.');
}
/**
* What is the element at the given index?
*
* @param Number aIdx
*/
at(aIdx) {
if (aIdx >= 0 && aIdx < this._array.length) {
return this._array[aIdx];
}
throw new Error("No element indexed by " + aIdx);
}
/**
* Returns the array representation of this set (which has the proper indices
* indicated by indexOf). Note that this is a copy of the internal array used
* for storing the members so that no one can mess with internal state.
*/
toArray() {
return this._array.slice();
}
}
exports.ArraySet = ArraySet;